Can you see it? Goldfish startle to polarized light stimuli

OTERO CORONEL, SANTIAGO; BERÓN DE ASTRADA, MARTÍN; MEDAN, VIOLETA

Montevideo

Congreso; International Congress of Neuroethology; 2016

International Society for Neuroethology

Aquatic environmentsare rich in polarized light patterns, creating a background polarization fieldagainst which objects diffusing or differentially reflecting polarized lightcan be viewed. To animals with a visual system sensitive to polarized lightsuch as goldfish, Carassius auratus,these cues could provide valuable information about its environment and be usedfor navigation and object detection.To test to whichextent polarization sensitivity its behaviorally functional for goldfish, werecorded their startle response (C-start) probability in response to anexpanding disc (loom) where the background was linearly polarized and the loomwas elliptically polarized. Goldfish startled to a polarized loom although witha smaller probability (35% startled, N=14) and longer latency (mean ± SD: 60±12 ms after end of loom) than when confronted with a black-over-whitecontrol loom (100% startled, 79 ± 33 ms before end of loom, N=14). Different neuralprocessing and/or lower saliency of polarized looms could be responsible forthe lower probability and longer response latency. Using non-polarized looms wetested if decreasing the contrast ratio (saliency) between the stimulus and thebackground reduced the response probability and increased latency of theresponse. Results show that progressively smaller contrast ratios have asmaller response probability (KW-ANOVA, p<0.001). Although latency torespond increases as the contrast ratio diminishes, it never reaches the valuesobserved with polarized looms. We speculate that theneural circuits implied in processing visible and polarized stimuli mightdiffer resulting in longer latency to respond to polarized stimuli.